The WKT2 string refers to a “Latitude of natural origin” parameter, but the corresponding PROJ string uses “lat_1” which, according to the PROJ doc, is a required parameter that means “First standard parallel”. My understanding of this
projection leads me to believe that the PROJ string is using the correct parameter name and the WKT2 is not. I have seen the same discrepancy with the Loximuthal projected CRS specified by ESRI: 54023. Is this correct? Is this a bug?
- PROJ.4 lat_1 name come from Snyder's "Map Projections: a working manual"
(https://pubs.usgs.gov/pp/1395/report.pdf), which uses the term "standard parallel" (also a few times "central parallel"), and the phi_1 notation. See page 138-140
- The WKT2 parameter name comes from the EPSG dataset, which uses the "Latitude of natural origin" terminology. See also EPSG Guidance Note 7-2
( https://drive.tiny.cloud/1/4m326iu12oa8re9cjiadxonharclteqb4mumfxj71zsttwkx/62018e48-9da4-43e7-b598-1202cd96ec9f ), page 38, which uses phi0 / "latitude of the origin".
Two different names, but that are mapped to the same maths. I'm not qualified to tell who is wrong / right
Regarding Loximuthal, I'm not sure where PROJ implementation comes from, but the maths do use lat_1. Regarding the WKT mapping, it is an artifact of GDAL WKT1 using "Latitude_of_origin" for the parameter name (no idea if that was appropriate), and thus the WKT2 equivalent has been mapped to "Latitude of natural origin" for consistency.
> Hi PROJ list,
> I've encountered a parameter discrepancy with a couple of ESRI CRS codes and
> I'm wondering if I've hit a bug. I'm using PROJ 6.2 and I get the following